Valuation and Qualifying Accounts [Schedule II] (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2012
Allowance for Doubtful Accounts, Current [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation allowances and reserves, beginning balance	$ 38	$ 46	$ 20
Valuation allowances and reserves, additions charged to expense/revenue	35	33	34
Valuation allowances and reserves, deductions	(30)	(41)	(8)
Valuation allowances and reserves, ending balance	43	38	46
Allowance for Product Returns [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation allowances and reserves, beginning balance	20	19	20
Valuation allowances and reserves, additions charged to expense/revenue	84	100	92
Valuation allowances and reserves, deductions	(80)	(99)	(93)
Valuation allowances and reserves, ending balance	24	20	19
Reserve For Rebates [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation allowances and reserves, beginning balance	15	17	11
Valuation allowances and reserves, additions charged to expense/revenue	110	112	104
Valuation allowances and reserves, deductions	(102)	(114)	(98)
Valuation allowances and reserves, ending balance	$ 23	$ 15	$ 17